Whereas the dipeptide sweetener known as aspartame (alpha-L-aspartyl-L-phenyalanine methyl ester) or APM has revolutionized the low calorie food and beverage industries, the sweetener is not without its drawbacks. Of major significance is the sweetener's instability in the presence of heat, moisture and alkaline environments. This instability has prevented its use in most if not all cooking and baking applications and is a factor that must be considered in products that require a long shelf life. Many attempts have been made using different coatings and/or physical/mechanical processing parameters to increase the stability of APM for this purpose and yet there still is much room for improvement.
U.S. Pat. No. 4,384,004 to Cea et al discloses the encapsulation of APM with one or a number of different coatings consisting of cellulose, cellulose derivatives, vinyl polymers, gelatin, zein, waxes and mixtures thereof in a ratio of coating material to APM of 1:1 or less. The APM is coated by conducting the APM particles in a stream of air that passes through a zone of atomized liquid droplets of the coating material thereby forming discrete layers about the APM particles under substantially anhydrous conditions. The stabilized APM particles are particularly useful in chewing gum applications.
U.S. Pat. Nos. 4,122,195 and 4,139,639 to Bahoshy et al propose to "fix" APM by preparing it with a material such as gum arabic or the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized starch acid-ester of a substituted dicarboxyllic acid by a spray-drying technique wherein the APM and film former are prepared in an emulsion. While the technique reportedly shows some improvement in shelf stability, relatively rapid breakdown of the APM still occurs.
U.S. Pat. No. 4,828,857 to Sharma et al discloses a sweetener delivery system wherein the sweetener core material is formed in an agglomerate hydrophobic matrix by spray congealing. The agglomerated matrix is selected from the group consisting of waxes, fatty acids and mixtures thereof. The agglomerated sweetener is then given a second coating of these hydrophobic materials and lecithin is added as a wetting agent to increase the affinity of the fat or wax for the APM crystals. Chewing gum and boiled hard candy are specifically taught applications for the sweetener delivery system.
U.S. Pat. No. 4,722,845 to Cherukuri et al discloses a stable, cinnamon-flavored chewing gum composition wherein a dipeptide or amino acid sweetener is protected from reacting with the degradative aldehydes of the flavor oil by encapsulating the sweetener in a mixture of fat and high melting point (106.degree.) polyethylene wax. The materials are coated onto the aspartame crystals using a modified spray congealing technique to form aggregated particles that may be mixed into the gum base for longer lasting shelf life stability.
U.S. Pat. No. 4,816,265 also to Cherukuri discloses chewing gum compositions containing APM that is encapsulated with a mixture of a low molecular weight polyvinyl acetate (PVA) and an emulsifier. The sweetener is blended into a homogeneous melted molten mass of PVA and the resultant mixture is a semi-solid mass which is cooled to a solid and ground into particles with a U.S. standard mesh size of 30 to about 200. The sweeteners are protected from adverse conditions such as moisture, PH, temperature and reactive chemicals such as flavor oils in the gums.
U.S. Pat. No. 4,704,288 to Tsau et al discloses a heat stabilized form of APM for baking applications. Aspartame is first granulated to particles with a U.S. mesh size of from about 8 to about 40 that are then coated with partially dehydrogenated vegetable oil. Both the type of fat and particle size are critical to the stability of the sweetener which may allegedly be used in cakes, cookies and other baked goods.
U.S Pat. No. 4,816,265 to Zibell discloses chewing gum with a delayed release, high potency sweetener such as aspartame. The APM is initially coated with modified cellulose such as hydroxypropyl methyl cellulose. The APM particles are then mixed with a zein solution with a pH of from 11.5 to 12.5. The damp mix is then dried to produce twice coated particles of the high intensity sweetener which allegedly enchance the shelf life stability of the sweetener and produce a delayed release of sweetness when this gum is chewed.
PCT Application No. PCT/US88/02398 also to Tsau discloses another heat stabilized form of APM wherein the dipeptide crystals are "spheronized" into dense, non-porous granules of substantially spherical shape within a narrow particle size range. The dense, spherical granules are preferably further encapsulated with a hydrophobic coating such as fats, starches, proteins and/or fibers and allegedly possess both stability against moisture, heat and acidic conditions as well as possessing a sustained release functionality for dispersion of the sweetener throughout the food matrix over time.
U.S. Pat. No. 4,588,612 to Perkins et al discloses the compaction of needle-like crystals of a material such as aspartame into a plurality of dense chips which are then ground to an average particle size of 20 to 400 standard U.S. mesh. The granules are then spread on a fluid bed spray reactor and encapsulated with a molten hydrogenated lipid or wax. The encapsulated aspartame granules are disclosed as being useful in baking applications since the encapsulating material essentially protects the granule from degradation that would otherwise result from the effects of heat and alkaline pH. The Perkins et al. invention is principally useful with water insoluble coatings which will allegedly protect the APM granules from moisture and heat that is present during baking.
It is an object of the present invention to provide a dipeptide sweetener composition with improved longer lasting shelf life stability. It is a further object of the present invention to provide a stabilized dipeptide sweetener that is compressed and encapsulated with a fat or wax coating in a 1:1 ratio to give it a long lasting shelf life stability. More particularly, it is an object of the present invention to provide an encapsulated compressed APM composition which, through dry granulation technology, possesses a longer lasting shelf life useful in chewing gum compositions where moisture, pH, and reactive flavor oils are adverse degradative factors.